Special thread

[charles-henri.vila]

Hello,

I have this device in picture and I would like to have your recommandations on how to make such a thread. It seems that the helical angle (not sure how to speak of it...) is relatively steep (much steeper than most available screws)

It is basically two tube adapters that screw into each other. In the end this seems to be similar to a water bottle right?

From all of the thread list i don't seem to find such a thread available. Should I try to find out how to make a custom one? Or is there an easier solution?

Thank you very much,

Best,

Charles

In the pictures you will see close up pictures of the threads of each piece and finally a global picture of the two pieces next to a nespresso coffee dose as a size comparison. I can definitely provide detailed dimensions if necessary. 

[lichtzeichenanlage]

There is a feature enhancement for threads at the road map but AFAIK not available right now. The video shows how to make custom threads by hand:

[chrisplyler]

Looks like a Double-Start (also known as 2-start or 2-lead) ACME thread.

Look it up and confirm your dimensions.

The Fusion thread tool doesn't have multi-start capability. Yet? You'll have to model them manually. Several youtube vids on how to do that.

[lichtzeichenanlage · Accepted solution]

@chrisplyler: Thanks for pointing out that this might be a 2 start thread. Perhaps this thread shows some solutions for this problem.

[chrisplyler]

I believe it is a double-start based on the picture showing the translucent female threaded bit directly from the side. You can clearly see in that image that two main diameters are directly opposed to each other.

Out of boredom I rendered up a single-start thread directly out of Fusion's thread tool...

[charles-henri.vila]

I thank you all for your answers - indeed it seems that with the coil tool I should be able to make this double start custom thread!

I have one more question though, when I screw the part in the other, it does not allow to screw all the way to the end of the coils - Instead after bearly a single full turn it seems to block, therefore causing a tight fit which I suppose accounts for the water tightness of this screw. 

I have been wondering if this is due to the double start or is it due to a coiling angle that is steeper than the female?

Thank you for your help 

[charles-henri.vila]

Or perhaps is it due to a multi start male and a single start female? I don't have the part with me but I will check first thing tomorrow morning

[chrisplyler]

I'm pretty sure the male thread is also double-start. I suspect the failure to screw all the way down is due to the slight taper (cone shape) of the inner tube that projects from the female threaded part. I suspect that fits into the male threaded part and creates the necessary seal.

[charles-henri.vila]

Thank you all

[Anonymous]

It is highly unlikely (impossible) that the threads form the seal, they just tighten the actual seal which will be at one of the thread ends (this may require a gasket).  For the threads to seal, they would have to fit too tightly to turn, there has to be some tolerance to allow the pieces to screw together.

For a single-start thread to mate to a double-start, its pitch would have to be double that of the double-start.  Then, only one of the two "coils" of the double-start will be contacted, with the in-between "coil" empty.